# CVE-2026-54089: File Browser authentication bypass via forged proxy headers

Source: https://junglewise.ai/threats/cve-2026-54089-file-browser-authentication-bypass-via-forged-proxy-headers  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-25. Updated: 2026-07-10  
License: CC BY 4.0 with a link back

CVE-2026-54089 · Severity: critical · CVSS 9.1 · Published 2026-06-25

File Browser is a web-based file management utility. When configured to use a reverse proxy for authentication, it fails to verify the source of identity headers, allowing any network-based attacker to impersonate any user, including administrators. This can lead to a total compromise of the file server, unauthorized access to all stored data, and the ability to execute arbitrary commands if shell features are enabled.

Technologies: [File Browser](https://junglewise.ai/threats/technologies/file-browser), [github.com/filebrowser/filebrowser (Go)](https://junglewise.ai/threats/technologies/github-com-filebrowser-filebrowser), [github.com/filebrowser/filebrowser/v2 (Go)](https://junglewise.ai/threats/technologies/github-com-filebrowser-filebrowser-v2). Vendors: [File Browser](https://junglewise.ai/threats/vendors/file-browser), [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-54089 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-54089 being exploited in the wild.

**How severe is CVE-2026-54089?** Critical severity, with a CVSS score of 9.1, published 25 June 2026.

**Which products and versions are affected?** File Browser >= 2.0.0-rc.1, >= 2.0.0-rc.1, <= 2.63.18; github.com/filebrowser/filebrowser (Go) SEMVER:introduced=0; github.com/filebrowser/filebrowser/v2 (Go) >= 2.0.0-rc.1, <= 2.63.18, SEMVER:introduced=2.0.0-rc.1, SEMVER:introduced=2.0.0-rc.1,last_affected=2.63.18.

**Is there a fix for CVE-2026-54089?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-54089 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-54089?** Check whether you run File Browser, github.com/filebrowser/filebrowser (Go) or github.com/filebrowser/filebrowser/v2 (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in the `ProxyAuth.Auth()` function within `auth/proxy.go`. When `auth.method` is set to `proxy`, the application unconditionally trusts the username provided in a configured HTTP header (e.g., `X-Remote-User`) without verifying the request's origin or requiring a shared secret. An attacker can reach the File Browser service directly (bypassing the intended reverse proxy) and provide an arbitrary username to receive a valid JWT. If the provided username does not exist, the application automatically creates a new account with default permissions. This allows for full administrative takeover and unauthorized access to the filesystem.

## Affected products

- File Browser File Browser >= 2.0.0-rc.1, <= 2.63.18

## Identifiers

- CVE-2026-54089
- GHSA-xqp3-jq6g-x3qm
- GO-2026-5966

## Timeline

- 2026-06-03: disclosed: Initial disclosure on GitHub Advisory Database
- 2026-07-10: advisory: Advisory updated with CVE-2026-54089

## References

- [https://api.github.com/users/Akokonunes](https://api.github.com/users/Akokonunes)
- [https://github.com/Akokonunes](https://github.com/Akokonunes)
- [https://api.github.com/users/Akokonunes/gists%7B/gist_id%7D](https://api.github.com/users/Akokonunes/gists%7B/gist_id%7D)
- [https://api.github.com/users/Akokonunes/repos](https://api.github.com/users/Akokonunes/repos)
- [https://avatars.githubusercontent.com/u/46332131?v=4](https://avatars.githubusercontent.com/u/46332131?v=4)
- [https://api.github.com/users/Akokonunes/events%7B/privacy%7D](https://api.github.com/users/Akokonunes/events%7B/privacy%7D)

## Related threats

- [File Browser symlink alias path traversal bypass](https://junglewise.ai/threats/cve-2026-90930-file-browser-symlink-alias-path-traversal-bypass)
- [File Browser authorization bypass in direct-upload endpoint](https://junglewise.ai/threats/cve-2026-90929-file-browser-authorization-bypass-in-direct-upload-endpoint)
- [File Browser subtitle conversion memory exhaustion](https://junglewise.ai/threats/cve-2026-90928-file-browser-subtitle-conversion-memory-exhaustion)
- [File Browser stale share link exposure in cross-user file deletion](https://junglewise.ai/threats/cve-2026-82236-file-browser-stale-share-link-exposure-in-cross-user-file)
- [File Browser path-based access control bypass in recursive operations](https://junglewise.ai/threats/cve-2026-73612-file-browser-path-based-access-control-bypass-in-recursive)